Effects of Cyclic Loading on the Mechanical Properties of Mature Bedding Shale

Guo, Yintong; Yang, Chunhe; Wang, Lei; Xu, Feng

doi:10.1155/2018/8985973

Cited by 17 publications

(18 citation statements)

References 13 publications

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“…In the future, if there are more data available, we could further fix some of the above-mentioned experimental parameters (e.g., confining pressure) to reduce the data scattering. 7 Geofluids the results from three papers: Singh [24], Haimson and Kim [25], and Guo et al [26]. Figure 14 summarizes the σ a /σ con versus N f relationship, and the relationship can be expressed as σ a σ con = 0:5443 N f À Á −0:1098 : ð10Þ…”

Section: Authors Rock Typementioning

confidence: 99%

Cyclic Injection to Enhance Hydraulic Fracturing Efficiency: Insights from Laboratory Experiments

Kang

Zhang²,

Fan

et al. 2020

Geofluids

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In hydraulic fracturing applications, there is substantial interest to reduce the formation breakdown pressure. Previous research results show that the cyclic injection method can be used to reduce that pressure. In this study, we conducted laboratory hydraulic fracturing experiments to apply cyclic injection to reduce the breakdown pressures of very tight and strong sandstones. Experimental results show that using cyclic injection the average breakdown pressure was reduced by 18.9% in very tight sandstones and by 7.18% in normal sandstones. This indicates that the effect of cyclic injection is more significant for stronger and tighter rocks. The experiments also reveal that the rock tensile strength plays a more important role in the formation breakdown pressure with a rock strength factor of 2.85. This suggests that the breakdown pressure is higher than expected. In addition, we empirically related the breakdown pressure reduction and the injection pressure amplitude to the number of injection cycles. The curve fitting results imply that the effect of cyclic injection is more important if the number of cycles or the injection pressure amplitude is increased. Based on the results of this research, the in-situ formation breakdown pressure can be reduced by applying the cyclic injection method, and the breakdown pressure reduction is more significant as the number of cycles increases.

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Section: Authors Rock Typementioning

confidence: 99%

Cyclic Injection to Enhance Hydraulic Fracturing Efficiency: Insights from Laboratory Experiments

Kang

Zhang²,

Fan

et al. 2020

Geofluids

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“…Previous research shows that the accumulation of irreversible deformation of rock, growth trend, and total fatigue under cyclic loading is directly related to fatigue damage [23]. According to the standard requirements [24,25], saturated rock uniaxial compressive strength is about 50 MPa, and the constant loop unloading test was carried out considering the frequent emergence of reservoir earthquake with low frequency and magnitude [26].…”

Section: E Cyclic Loading and Unloading Test Schemementioning

confidence: 99%

The Dynamic Response Law of Bank Slope under Water‐Rock Interaction

Zhang

Deng

Wang

et al. 2018

Advances in Civil Engineering

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During the reservoir operation process, the long-term security and stability of the bank slope is affected by dynamic response characteristics of its seismic action directly. Aimed at the typical bank slope existing in the actual reservoir environment, an experiment considering reservoir water level fluctuation and soaking-air-drying cyclic water-rock interaction has been designed and conducted while the cyclic loading test was performed in different water-rock cycles. Research results indicate the following: Firstly, in the process of water-rock interaction, the dynamic characteristics of sandstone show evident degradation trend, with the increase of the damping ratio and Poisson's ratio and decrease of dynamic elastic modulus, and the former six water-rock cycle degradation effects are particularly obvious. Secondly, the numerical analog computation analysis of dynamic response in typical bank slope shows that as the water-rock interaction period is increased, the dynamic response of the slope hydro-fluctuation belt zone increases gradually, while the other parts weaken. irdly, under the long-term water-rock interaction process, the hydrofluctuation belt zone gradually becomes a "soft layer" which is sensitive to the earthquake effect and dynamic response, resulting in a direct influence on long-term seismic performance of the bank slope. erefore, it is necessary to make better protection for the bank slope hydro-fluctuation belt zone.

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“…Wang et al [21] conducted multistage creep tests on shale samples under different temperatures and confining pressures to study the effects of temperature, confining pressure, and precrack on shale creep characteristics. Guo et al [22] conducted uniaxial compression tests and acoustic emission tests on shale samples with different bedding surface dip angles at different temperatures and studied the effect of temperature on the physical and mechanical properties of shale. Yang et al [23] conducted dynamic compression tests on shale specimens in the temperature range of 20~220°C, studied the mechanical properties of shale at different temperatures, and analyzed the dynamic deformation and failure process of shale.…”

Section: Introductionmentioning

confidence: 99%

Study on the Damage Evolution Process and Fractal of Quartz-Filled Shale under Thermal-Mechanical Coupling

Song

et al. 2021

Geofluids

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Filling of brittle minerals such as quartz is one of the main factors affecting the initiation and propagation of reservoir fractures in shale fracturing, in order to explore the failure mode and thermal damage characteristics of quartz-filled shale under thermal-mechanical coupling. Combining the theory of damage mechanics and thermoelasticity, RFPA2D-Thermal is used to establish a numerical model that can reflect the damage evolution of shale under thermal-solid coupling, and the compression test under thermal-mechanical coupling is performed. The test results show that during the temperature loading process, there is a temperature critical value between 60°C and 75°C. When the temperature is less than the critical temperature, the test piece unit does not appear obvious damage. When the temperature is greater than the critical temperature, the specimen unit will experience obvious thermal damage, and the higher the temperature, the more serious the cracking. Under the thermal-mechanical coupling of shale, the tensile strength and elastic modulus of shale show a decreasing trend with the increase of temperature. The failure modes of shale under thermal-solid coupling can be roughly divided into three categories: “V”-shaped failure (30°C, 45°C, and 75°C), “M”-shaped failure (60°C), and inverted “λ”-shaped failure (90°C). The larger the fractal dimension, the more complex the failure mode of the specimen. The maximum fractal dimension is 1.262 when the temperature is 60°C, and the corresponding failure mode is the most complex “M” shape. The fractal dimension is between 1.071 and 1.189, and the corresponding failure mode is “V” shape. The fractal dimension is 1.231, and the corresponding failure mode is inverted “λ” shape.

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Effects of Cyclic Loading on the Mechanical Properties of Mature Bedding Shale

Cited by 17 publications

References 13 publications

Cyclic Injection to Enhance Hydraulic Fracturing Efficiency: Insights from Laboratory Experiments

Cyclic Injection to Enhance Hydraulic Fracturing Efficiency: Insights from Laboratory Experiments

The Dynamic Response Law of Bank Slope under Water‐Rock Interaction

Study on the Damage Evolution Process and Fractal of Quartz-Filled Shale under Thermal-Mechanical Coupling

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